Proton-Conducting Electrolytes

M. Eikerling, Y.l. Kharkats, A.A. Komyshev, and Y.M. Volfkovich. Phenomenological theory of electro-osmotic effect and water management in polymer electrolyte proton-conducting membranes. Journal of the Electrochemical Society 145, 2684—2699 1998. 

Aromatic condensing polymers with fragments of benzimidazole or quinoxaline as base in electrolytic proton-conducting membranes 02UK862. 

As with oxygen ion-conducting electrolytes, proton conduction in these electrolytes occurs only within a limited range of hydrogen partial pressures. In addition, as they are oxides, oxygen defects can occur. Figure 13.6 shows the predominant defects in indium-doped calcium zirconate, which were calculated based on an extrapolation of conductivity measurements [79]. Hydrogen conduction occurs by interstitials H ... 

Currently used electrode-catalysts (anode and cathode) consist of an assembly of metallic nanoparticles usually deposited on an electronic conducting substrate and embedded in a hydrated membrane [10, 11], which is the polymer electrolyte proton-conductive material (Figure 17.1). What differs between cathode and anode is the catalyst material, and also the significantly slow kinetics of the cathode oxygen reduction reaction compared to that of the anode hydrogen oxidation reaction. For this reason, several... 

Smirnova, A., Prakash, R, Phillips, R. and Sammes, N.M. (2(K)4) Electrolyte proton-conductive materials for protonic ceramic fuel cells (PFCFs). Proceedings of the sixth European Solid Oxide Fuel Cell Forum, 28 June to 2 July 2004,... 

Polymer Electrolyte Fuel Cell. The electrolyte in a PEFC is an ion-exchange (qv) membrane, a fluorinated sulfonic acid polymer, which is a proton conductor (see Membrane technology). The only Hquid present in this fuel cell is the product water thus corrosion problems are minimal. Water management in the membrane is critical for efficient performance. The fuel cell must operate under conditions where the by-product water does not evaporate faster than it is produced because the membrane must be hydrated to maintain acceptable proton conductivity. Because of the limitation on the operating temperature, usually less than 120°C, H2-rich gas having Htde or no (

Ren, X. Springer, T. E. and Gottesfeld, S. (1998). Direct Methanol Fuel Cell Transport Properties of the Polymer Electrolyte Membrane and Cell Performance. Vol. 98-27. Proc. 2nd International Symposium on Proton Conducting Membrane Euel Cells. Pennington, NJ Electrochemical Society. 

T.I. Politova, V.A. Sobyanin, and V.D. Belyaev, Ethylene hydrogenation in electrochemical cell with solid proton-conducting electrolyte, Reaction Kinetics and Catalysis Letters 41(2), 321-326 (1990). 

A considerable decrease in platinum consumption without performance loss was attained when a certain amount (30 to 40% by mass) of the proton-conducting polymer was introduced into the catalytically active layer of the electrode. To this end a mixture of platinized carbon black and a solution of (low-equivalent-weight ionomeric ) Nafion is homogenized by ultrasonic treatment, applied to the diffusion layer, and freed of its solvent by exposure to a temperature of about 100°C. The part of the catalyst s surface area that is in contact with the electrolyte (which in the case of solid electrolytes is always quite small) increases considerably, due to the ionomer present in the active layer. 

Electrolytes for Electrochromic Devices Liquids are generally used as electrolytes in electrochemical research, but they are not well suited for practical devices (such as electrochromic displays, fuel cells, etc.) because of problems with evaporation and leakage. For this reason, solid electrolytes with single-ion conductivity are commonly used (e.g., Nafion membranes with proton conductivity. In contrast to fuel cells in electrochromic devices, current densities are much lower, so for the latter application, a high conductivity value is not a necessary requirement for the electrolyte. 

Similarly, the cell voltage across a proton-conducting electrolyte subjected to a hydrogen pressure gradient is given by the Nemst equation ... 

This electrochemical decomposition requires about 1 V at the electrode surface. To drive the protons into the WO3 film, a proton-conducting electrolyte, typically... 

The main components of a PEM fuel cell are the flow channels, gas diffusion layers, catalyst layers, and the electrolyte membrane. The respective electrodes are attached on opposing sides of the electrolyte membrane. Both electrodes are covered with diffusion layers, and the flow channels/current collectors. The flow channels collect current from the electrodes while providing the fuel or oxidant with access to the electrodes. The gas diffusion layer allows gases to diffuse to the electro-catalysts and provides electrical contact throughout the catalyst layers. Within the anode catalyst layer, the fuel (typically H2) is oxidized to produce electrons and protons. The electrons travel through an external circuit to produce electricity, while the protons pass through the proton conducting electrolyte membrane. Within the cathode catalyst layer, the electrons and protons recombine with the oxidant (usually 02) to produce water. 

PEM Proton-exchange-membrane fuel cell (Polymer-electrolyte-membrane fuel cell) Proton- conducting polymer membrane (e.g., Nafion ) H+ (proton) 50-80 mW (Laptop) 50 kW (Ballard) modular up to 200 kW 25-=45% Immediate Road vehicles, stationary electricity generation, heat and electricity co-generation, submarines, space travel... 

X-Ray Photoelectron Investigation of Phosphotungstic Acid as a 159 Proton-Conducting Medium in Solid Polymer Electrolytes Clovis A. Linkous, Stephen L. Rhoden, and Kirk Scammon... 

GDE s may be interesting for synthesis cells as depolarized electrodes (e.g. [48]). A hydrogen-consuming anode will work at a low potential that avoids undesired anodic oxidations (e.g. no chlorine evolution in presence of chlorides). In order to reject an excess of the electrolyte from the GDE structure, a proton-conducting membrane (Nafion ) between the GDE and the electrolyte can be used ( Hydrina , De Nora Spa. [49]). 

Zawodzinski, T. A., Davey, J., Valerio, J. and Gottesfeld, S. 1995. The water-con-tent dependence of electro-osmotic drag in proton-conducting polymer electrolytes. Electrochimica Acta 40 297-302. 

Miyatake, K., Zhou, H., Matsuo, T., Uchida, H. and Watanabe, M. 2004. Proton conductive polyimide electrolytes containing trifluoromethyl groups Synthesis, properties, and DMFC performance. Macromolecules 37 4961 966. 

Jeske, M., Soltmann, C., Ellenberg, C., Wilhelm, M., Koch, D. and Grathwohl, G. 2007. Proton conducting membranes for the high temperature-polymer electrolyte membrane-fuel cell (HT-PEMFC) based on functionalized polysiloxanes. 

Gasa, J. V., Weiss, R. A. and Shaw, M. T. 2006. Influence of blend miscibility on the proton conductivity and methanol permeability of polymer electrolyte blends. Journal of Polymer Science Part B 44 2253-2266. 

---